Field of the Invention
Hemostatic clips and surgical staplers have been used increasingly in recent years to supplant prior art techniques used to suture and close wounds or to tie off blood vessels during surgery or other traumatic medical care. Hemostatic clips and surgical staples (hereinafter "clips") may be applied using any of a number of tools known in the art. Generally, such a tool includes opposed jaws which crimp the U-shaped clip flat across the tissues to be sutured or tied off. Normally, the tool or applicator that is used to dispense such clips is capable of dispensing a plurality of clips that are fed serially to the jaws.
In most of the tools currently used to dispense such clips, a compression spring is used to supply the force needed to advance the clips in queue towards the jaws until the endmost clip is in position to be dispensed. Although a compression spring generally supplies adequate force to advance the clips toward the jaws in the existing tools, one disadvantage of using a compression spring is that a compression spring occupies a relatively large amount of space within the tool. The tool space that currently is used to house a compression spring could be used more advantageously to hold additional clips. The added clip capacity would reduce the number of times that the tool would have to be reloaded during surgery or other traumatic medical care.
Another disadvantage of using a compression spring to advance the clips toward the jaws is that the amount of force exerted by a compression spring on a queue of clips is not uniform. For example, the pressure that a compression spring exerts on the first clip dispensed from a queue of forty clips will be much greater than the pressure exerted by that same compression spring on the thirty-fifth or fortieth clip in queue. When the first clip in queue is dispensed, thirty-nine other clips maintain the compression spring in a compressed state. The pressure exerted by a highly compressed spring on the first few clips in queue could cause the legs of those first clips to spread during dispensing. This spreading of the legs could prevent the first clip(s) from feeding smoothly into the jaws of applicator.
In contrast, by the time that the thirty-fifth or fortieth clip in queue is dispensed, very few clips remain in queue to maintain the compression spring in its compressed state. In a relatively decompressed state, a compression spring cannot exert the same amount of pressure on the thirty-fifth or fortieth clip in queue as it exerts on the first clip in queue. In fact, the pressure exerted by a compression spring on the last clip(s) in queue may be insufficient to permit those clips to be dispensed from the queue at all.
It therefore would be advantageous to provide an applicator with a means to exert substantially constant pressure on all of the clips in queue. It also would be advantageous to reduce the amount of space required to house the mechanism used to supply such constant pressure.
In addition, it recently has been discovered that clips having a rough or abrasive surface may have enhanced gripping ability and/or may promote tissue in-growth, which helps to hold the clip in place and also promotes healing. Thus, it sometimes is advantageous to coat the clips that will be dispensed by such an applicator with a rough or abrasive material.
However, it also has been discovered that rough or abrasive clips tend to adhere more tightly to one another in queue. In fact, when an applicator is used to dispense abrasive clips, the endmost clip often clings so tightly to the legs of the adjacent clip that the endmost clip cannot be dispensed. The result is a clogged applicator, which is useless until the clog is freed. Of course, clogging of an applicator during traumatic medical care is extremely undesirable.
It therefore would be advantageous to provide an applicator with a means for more effectively disengaging an endmost clip from a column of rough or abrasive clips.